1. Adefolalu, D. O., 1986: Further aspects of sahelian drought as evident from rainfall regime of Nigeria.Arch. Met. Geoph. Biocl., Ser. B 36, 277?295.
2. Albergel, J., Carbonnel, J. P., Grouzis, M., 1984/85: Péjoration climatique au Burkina Faso. Cahiers de l'Orstom, Série Hydrologique,XXI (1), 3?19.
3. Anonymous, 1979: Symposium on drought in Botswana. Botswana Society in Collaboration with Clark University Press, 305.
4. Beran, M. A., Rodier, J. A., 1985: Hydrological aspects of droughts. A contribution to the IHP. Unesco-WMO, Paris, 149.
5. Bowden, M. J., Kates, R. W., Kay, P. A., Riebsame, W. E., Warrick, R. A., Johnson, D. L., Gould, H. A., Weiner, D., 1981: The effect of climatic fluctuations on human populations: two hypotheses. In: Wigley, T. M. L., Ingram, M. J., Farmer, G. (eds.),Climate and History, Studies in Past Climates and Their Impact on Man. Cambridge University Press, p. 479?513.